Where is screensaver documentation?

Basically any component that accepts user input is not supported in a screensaver, as it wouldn't make sense. Below is the list of such components. If you try to create one of these in a screensaver, you should see a message like this on the debug console:

** ERROR ** Cannot create roParagraphScreen: Not supported in a screen saver.

You're right, this should be added to the documentation.

roAudioPlayer
roChannelStore
roCodeRegistrationScreen
roGridScreen
roKeyboardScreen
roListScreen
roMessageDialog
roOneLineDialog
roParagraphScreen
roPinEntryDialog
roPosterScreen
roSearchHistory
roSearchScreen
roSpringboardScreen
roTextScreen
roVideoPlayer
roVideoScreen

--Mark

So where is the documentation?
I have specific question too, from viewtopic.php?f=34&t=66492&p=425734#p425734 i wonder:

"EnTerr" wrote:
... my understanding so far is that the active channel gets paused and screen saver runs until interrupted, is that not the case? In particular i am foggy on what happens if channel Foo is running in regular mode when screen saver kicks-in and the chosen screensaver is Foo as well (i.e. Foo advertised itself as screen saver and was chosen in Settings); is new context spawned - or call is forced within regular Foo - or no saver is called - or crash happens?

Hi EnTerr,

The active channel is not paused while a screensaver runs, the Screensaver runs in a separate thread and the channel continues to run. If the Screensaver it is signed with the same Dev ID as the channel, you will be able to pass data back and forth between the running channel and screensaver by writing files to the shared tmp:/ folder.

As far as docs go, we don't have detailed "how to" but it is fairly easy to figure out from the examples in the SDK.

I've filed a bug on the missing docs on your behalf.

-Joel

"RokuMarkn" wrote:
Basically any component that accepts user input is not supported in a screensaver, as it wouldn't make sense. Below is the list of such components. If you try to create one of these in a screensaver, you should see a message like this on the debug console:

** ERROR ** Cannot create roParagraphScreen: Not supported in a screen saver.

RokuMarkn -
your explanation is great, glad you listed the no-no components, i ran into this too - got "Screen preview failed" with roParagraphScreen facade.

But there is NO ERROR shown on the console. In fact, seems that no PRINT statements from the screensaver code make it to the console whatsoever. Is this by design (e.g. since another thread is hogging the console)? Can it be circumvented, so i can see debug info while testing the screensaver?

"EnTerr" wrote:

"RokuMarkn" wrote:
Basically any component that accepts user input is not supported in a screensaver, as it wouldn't make sense. Below is the list of such components. If you try to create one of these in a screensaver, you should see a message like this on the debug console:

** ERROR ** Cannot create roParagraphScreen: Not supported in a screen saver.

RokuMarkn -
your explanation is great, glad you listed the no-no components, i ran into this too - got "Screen preview failed" with roParagraphScreen facade.

But there is NO ERROR shown on the console. In fact, seems that no PRINT statements from the screensaver code make it to the console whatsoever. Is this by design (e.g. since another thread is hogging the console)? Can it be circumvented, so i can see debug info while testing the screensaver?

I think it was already answered in your other thread, but can't hurt to post it here too... you can telnet to port 8087 to see the output from the screensaver thread.

"TheEndless" wrote:
I think it was already answered in your other thread, but can't hurt to post it here too... you can telnet to port 8087 to see the output from the screensaver thread.

Yes, telnet 8087 is the screensaver console, now i know. It can be ^C interrupted (with the usual 50/50-chance-of-staying-in-debug bug).

"** ERROR ** Cannot create roParagraphScreen: Not supported in a screen saver." pops as a warning there.

"RokuJoel" wrote:
The active channel is not paused while a screensaver runs, the Screensaver runs in a separate thread and the channel continues to run. If the Screensaver it is signed with the same Dev ID as the channel, you will be able to pass data back and forth between the running channel and screensaver by writing files to the shared tmp:/ folder.

Thank you, RokuJoel - that short explanation helped me a lot to grasp how sandboxing is done in this case, so credit due.

Including to imply (then test) that variables are not shared between main() and RunScreenSaver(). Since there is no shared memory, we should not talk about "threads" from outside developer point of view; logically these are more of (pseudo)processes, even if physically implemented by C threads in Roku executable.

Besides tmp:/, I found another means for main/screensaver "interprocess" communication: roRegistry. Registry i think is better choice for fast messaging between the two, since all happens in RAM and there is no need to reg.flush() - one can do reg.write() and the other right away reg.read() and see the result. Let me know if there is issue with relying on that behavior.

Adoration.

Why is it, after nearly 8 years of this forum, is it literally impossible to add an anti-spam filter?

"EnTerr" wrote:
Besides tmp:/, I found another means for main/screensaver "interprocess" communication: roRegistry. Registry i think is better choice for fast messaging between the two, since all happens in RAM and there is no need to reg.flush() - one can do reg.write() and the other right away reg.read() and see the result. Let me know if there is issue with relying on that behavior.

This technique is being reviewed by RokuMarkN for thread-safety, i.e. what happens when one both screensaver and main app write to the same registry key at the same time, or one is reading at the same moment the other is writing.

- Joel